Recent theoretical analyses have posited a developmental increase in children's tendency to exercise selective attention and ignore extraneous information. The proposed research will examine developmental trends as measured by three paradigms bearing on this issue--distractibility, incidental learning, and component selection. A series of studies is planned for each of these three aspects of attention, and the variables to be included in each case will be ones suggested by theory and previous research to influence the nature of the attentional processes that children employ. In the study of distractibility, variables associated with the distractor are: (a) modality, (b) meaningfulness, (c) duration, (d) instructions regarding its function, and (e) (for visual distraction) proximity to the task stimuli. The criterion task used to measure the effects of distraction will vary in (a) difficulty and (b) involvement of verbal processes. The study of incidental learning will include variation in (a) the relation between the stimulus components, (b) instructions and training concerning the incidental cues, and (c) the type of incidental memory assessed. The distracting effect of incidental cues will also be measured. Variables to be included in the study of component selection are: (a) the relative salience of the stimulus components employed, (b) the relation between components, and (c) the degree to which the task requires attention to a single component. The project will include five studies of distractibility, four of incidental learning, and three of component selection. Each study will incorporate a subset of the variables listed and will include an average of 600 children at ages 5, 8, and 11. A brief description of the initial study in each area is provided, including details regarding methodology and data analysis.